176 COMPARATIVE 
ZOOLOGY. 
the Clam, it is found at the base of the foot ; some Grass- 
hoppers have it in the forelegs; and in many Insects it is 
\ fo) D 
ul i) i 
6b 
il 
Fic. 148.—Brain and Auditory Apparatus of the Cuttle-fish: a, b, brain; c, auditory 
apparatus; d, the cavity in which it is lodged; e, f, g, eyes; 1, 2, 3, otoliths. 
on the wing. Lobsters, Crabs, 
auditory sacs at the base of the 
A complex organ of hearing, 
and most Insects have the 
antenne.’” 
located in the head, exists 
in all Vertebrates, save the very lowest Fishes. As com- 
plete in Man, it consists of the 
re. 149.—Section of Human Ear: a, external 
ear, with auditory canal; b, tympanic cavi- 
ty containing the three bones; c, hammer, 
and its three muscles, d, e, f; g, tympanic 
membrane, or head of the drum; hk, Eusta- 
chian tube leading to the pharynx; 7, laby- 
rinth, with semicircular canals and cochlea 
visible. 
cates with the external air by 
following parts: Ist. The 
external ear (which is pe- 
culiar to Mammals); the 
auditory canal, about an 
inch long, lined with hairs 
and a waxy secretion, and 
closed at the bottom by a 
membrane, called tympa- 
num, or “drum of the 
ear.” 2d. The middle 
ear, containing three little 
bones (the smallest in the 
body), malleus, incus, and 
stapes, articulated togeth- 
er. The cavity communi- 
means of the Eustachian 
tube, which opens at the back part of the mouth. 3d. 
